What are the clinical examination provocative tests to distinguish between sciatica and piriformis syndrome?

Distinguishing Sciatica from Piriformis Syndrome: Key Provocative Tests

The two most clinically useful provocative tests to distinguish between sciatica and piriformis syndrome are the straight leg raise (SLR) test and the FAIR test (Flexion, Adduction, and Internal Rotation of the hip)—a negative SLR with positive FAIR test strongly suggests piriformis syndrome rather than radiculopathy. 1

Understanding the Diagnostic Distinction

Straight Leg Raise (SLR) Test

• In true sciatica from disc herniation: The SLR test is typically positive, with 91% sensitivity for detecting lumbar disc herniation causing nerve root compression 2
• In piriformis syndrome: The SLR test is typically negative or normal, as there is no nerve root tension from disc pathology 1
• The test is performed by flexing the hip with the knee extended, and is positive when radiating leg pain is reproduced between 30-70 degrees of elevation 3

FAIR Test (Freiberg Sign) and Related Piriformis-Specific Maneuvers

• Flexion, Adduction, and Internal Rotation (FAIR) of the hip: This maneuver stretches the piriformis muscle and reproduces symptoms in piriformis syndrome 1
• Pace sign: Resisted abduction and external rotation of the hip causes pain by contracting the piriformis muscle 1
• Direct palpation: Tenderness over the piriformis muscle near the greater sciatic notch is characteristic of piriformis syndrome 1, 4
• These maneuvers are positive in piriformis syndrome because they increase tension through or around the piriformis muscle where the sciatic nerve is compressed 1

Clinical Algorithm for Differentiation

Key Distinguishing Features

Sciatica from Radiculopathy:

• Positive SLR test (91% sensitivity) 2
• May have dermatomal sensory changes in L4, L5, or S1 distributions 2
• May have motor weakness: knee weakness (L4), foot/toe dorsiflexion weakness (L5), or plantarflexion weakness (S1) 2
• May have reflex changes: diminished knee reflex (L4) or ankle reflex (S1) 2

Piriformis Syndrome:

• Negative or normal SLR test 1
• Positive FAIR test (hip flexion, adduction, internal rotation reproduces symptoms) 1
• Positive Pace sign (resisted hip abduction/external rotation causes pain) 1
• Buttock pain that worsens with sitting 1, 4
• External tenderness near the greater sciatic notch 4
• Normal neurological examination (no focal motor weakness or reflex changes) 1

Critical Clinical Pitfalls

Common Diagnostic Errors

• Over-reliance on imaging: Piriformis syndrome typically shows normal lumbar spine MRI and normal neurodiagnostic studies 1, 5
• Assuming all sciatica is discogenic: Piriformis syndrome is a nondiscogenic cause of sciatica that requires different management 1, 6
• Misinterpreting negative SLR: A negative SLR does not rule out sciatic nerve pathology—it helps distinguish peripheral nerve entrapment (piriformis syndrome) from nerve root compression (radiculopathy) 1, 4

The Diagnostic Quartet for Piriformis Syndrome

The four defining features are 4:

1. Buttock pain
2. Pain aggravated by sitting
3. External tenderness near the greater sciatic notch
4. Pain on any maneuver that increases piriformis muscle tension (FAIR test, Pace sign)

When Physical Examination Findings Conflict

• If both SLR and FAIR tests are positive, consider coexisting pathology or alternative diagnoses 5
• If neurological deficits are present (motor weakness, reflex changes), radiculopathy is more likely regardless of FAIR test results 1
• Advanced imaging with MRI of the pelvis may show piriformis muscle hypertrophy, though this is not always present 7
• The crossed SLR test (pain when raising the unaffected leg) has 88% specificity for disc herniation and would not be positive in isolated piriformis syndrome 2